Advances in technology have resulted in an increasing demand for system-on-chip products where both analog and digital signal processing are desirable. For example analog circuits capture an analog signal from the surrounding environment and transform the signal into bits which are then transformed into signals for driving digital circuitry and output functions. Increasingly it is advantageous to have both the analog circuitry and digital circuitry in close proximity, for example in the form digital blocks and analog blocks of circuitry which function together to implement the function of the system, also referred to as mixed mode systems.
For example, passive components (inductors, resistors, and capacitors) in analog/mixed-signal design passives are used for a wide variety of functions including tuning, filtering, impedance matching, and gain control. For example MIM capacitors are critical in several mixed signal integrated circuits such as analog frequency tuning circuits, switched capacitor circuits, filters, resonators, up-conversion and down-conversion mixers, and A/D converters.
In metal-insulator-metal (MIM) structures, which are included in analog circuitry building blocks, smaller capacitors are desirable from the standpoint of lower power consumption and increased feature density in a semiconductor device (chip).
Many analog and mixed mode systems rely on precise reproducibility in the electronic properties of circuit component structures, such as MIM structures, to achieve the electrical matching of the various circuitry components. Electronic mismatch of circuitry components results in reduced signal processing quality and is adversely affected by deviations in critical dimensions between components which is exacerbated by the increased number of processing steps generally required for producing the same component having different passive values, for example capacitance.
One continuing problem with the integration of analog and digital circuitry blocks is the increase in power consumption. The design constraints that inform the design of digital blocks include the need for fast signal transmission and low power consumption. On the other hand in analog circuitry, the design constraints are strongly informed by the actual electrical performance of the passive components, for example the capacitance value of capacitors. For example, an integrated circuit requiring a number of MIM capacitors, each MIM capacitor occupies a given area projected through the volume of a chip. In particular, the presence of components underlying or overlying an MIM capacitor is not desirable due to parasitic influences on the capacitance value of the MIM. As a result, passive components generally occupy a large amount of space in CMOS analog integrated circuitry, leading to higher processing costs. For example, assuming the capacitor dielectric and thickness remains the same, about twice the area of capacitor dielectric is need to double the capacitance value.
There is therefore a continuing need in the semiconductor device processing art for improved MIM capacitor structures and manufacturing processes to achieve lower cost production and higher feature density while maintaining capacitance value precision.
It is therefore an object of the invention to provide an improved MIM capacitor structure and manufacturing processes to achieve lower cost production and higher feature density while maintaining capacitance value precision, while overcoming other deficiencies and shortcomings of the prior art.